Surgery for fixing a diseased part or lesion of the bone by tightening medical screws has so far been performed widely.
For a disease involving instability of the spine, such as spondylosis deformans or spinal injury, in particular, surgery for fixing the position of the spine by sticking medical screws made of titanium into the spine is widely performed.
This surgical technique, however, poses difficulty in ensuring the safety of the surgery sufficiently only with the use of the existing tool, because not only the shape of the bone itself, but the position of screw fixation and the path of sticking the screw are different according to a patient, symptoms and the contents of therapy.
With the surgery of spine fusion, therefore, injury to the blood vessel or nerve occurs when a spinal fusion screw is inserted into the spine, unless the site of insertion, the direction of insertion and the depth of insertion of the spinal fusion screw into the spine are strictly determined.
Currently, when a surgery using the spinal fusion screw is performed, the position, direction and depth of insertion of the spinal fusion screw are planned preoperatively using a fluoroscope, a bored hole in a predetermined direction, and of a predetermined depth is formed by means of a drill, and the spinal fusion screw is screwed into the bored hole to fix the spine.
Accurate boring along the insertion direction from the accurate position of insertion of the spinal fusion screw by use of this method, however, requires advanced skills. If boring is inaccurate, precise insertion of the spinal fusion screw into the spine is impossible. Even when the bored hole is formed correctly, it is likely for the medical screw to deviate from the planned path, if the medical screw fails to be screwed in from the correct direction after the boring procedure. If the predetermined diameter of the bored hole is large, in particular, a fine bored hole is first provided, and then a bored hole with a larger diameter is provided, with the fine hole being used as a guide. However, it involves great difficulty to bring the direction of the second drilling into exact conformity with the direction of the first drilling.
Patent Document 1 discloses a surgical method using a registration template for use in a medical navigation system-guided surgery.
With this surgical method, the position of the leading end of a medical instrument, such as a surgical knife or a drill, in an image of an operative site on a display is confirmed on the display, and surgery is performed, with knowledge of a state where the leading end of the medical instrument arrives at the correct position. The registration template is designed for such surgery, and is not a bone fixing template for setting the drilling position, direction and depth of the present invention precisely, and facilitating the screwing-in and tightening of a medical screw.
Patent Document 2 discloses a method for producing an artificial bone model which is manufactured by selective laser sintering to be described later, and which has cuttability closely resembling that of a natural bone.
Patent Document 3 discloses an instrument for treatment of a patient with impairment of the osseous semicircular canals, the instrument produced by use of a stereolithographic apparatus to be described later; and a method for manufacturing the instrument.
Patent Document 4 discloses a method for producing a soft blood vessel model for surgical simulation by use of ink-jet rapid prototyping to be described later.